Compensated motor.



No. 876,924. PATENTED JAN. 21, 1908.

' E. P. W. ALEXANDERSON,

OOMPENSATED MOTOR.

' APPLICATION FILED JULY 19. 1906.

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Wifimsses PATENTBD JAN. 21, 1908. B. F. W. ALEXANDBRSON.

COMPBN SATED MOTOR.

APPLICATION FILED JULY 19, 1906.

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Inven im Ernsf FW. A! xanderson Wi (nesses placed in slots at or near tUNITEDSTATES PATENT orrron ERNST F. W. ALEXANDERSON, OF SOHENE CTADY,NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEWYORK.

COHPEHSATED MOTOR.

Application filed July 19. 1906. Serial No. 328.861.

T all whom it may concern:

Be it known that l, ERNST F. W. ALEXAN- DERSON, a subject of the King ofSweden, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful IIBPIOVQHXGIIES inCompensated Motors, of which the following is a specification.

My invention relates to electric motors or the commutator type providedwith compensating windings. Such windings, though frequently used ondirect-current motors, are particularly advantageous on alternaticurrent motors of the commutator type, b tl'i for the purpose ofneutralizing armature selfinduction and for improving commutation, whichpresents more difliculties in alternating-current motors than in.direct-current machines, on account of the relatively weaker field whichis ordinarily used on alternatingcurrent motors, and because of thealternating-flux threading the short-circuited coil in commutation.

Compensating windin s are ordinarily 1e inner face of the fieldstructure. Since alternating current commutator motors are usuallydesigned for operation on low voltage, the current capacity, andconsequently the size, of the compensating winding, which is connectedin series with the armature, must be large. If there were sufficientspace on the inner periphery of the field structure, the compensatingwinding could be wound with only a single conductor per slot, whichgives a maximum efiiciency, so far as material is concerned, since asmaller proportion of the slot-space is then required for insulation. Inthe smaller sizes of machines, however, there is not room enough. on thefield structure for the number of slots that would be required for thisconstruction. But when two or more conductors per slot are used, muchspace is lost in insulation, and also the end-connections of thecompensating winding are complicated and hero to make, since theconductors are of considerable size and must he properly insu lated fromeach other.

By one c or per slct for the compensating erebv o taming eiiiSpecification of Letters-Patent.

' Patented Jan. 21, 1908.

. transformer the switch is thrown a c contact-Larger ccntrciiing switchwith a smaller number of turns than the effective turns of the armature,and in arm ing a plurality of armatures in parallel each other andplacing the compensating windings in series with each other and with thearinatures. Thus, for instance, if two compensated motors are arrangedeach with half the usual number of turns in their compensating windings,then by connecting the two armature windings in parallel with eachother, and the two compensating windings in. series, each compensatingWinding carries twice as much current as the armature, so that theproper proportion of ampere turns is secured.

My invention will best be understood by reference to the accompanyingdrawings, in which Figure lshows diagrammatically a plurality.ofcompensated motors arranged to be operated in accordance with myinvention; Figs. 2, 3 and 4 show the circuit-connections obtained bymeans of the controlling switches of Fig. 1; and Fig. 5 shows a motorhaving a compensated winding arranged with one conductor per slot, inaccordance with my invention. 1

Referring first to Fig. 5, Are resents the armature, and F the fieldcoil 0' an electric motor of the commutator type. C re resents thecompensating winding, whic is carried in slots at the face of the fieldpoles, and which is formed with one conductor per slot.

Now, refeiying to Fig. '5, .l have shown four inotors,.th'e armature ofthefirst motor being indicated by A, the second by A, etc. These motorsmay re resent the equi ment of an electric car or ocomotive whic it isdesired to operate on both direct and alternati -current. orcoilector-shoe, which is arranged to he connected through a switch E tothe controlling switch G, either directly or through, theauto-transformer D. Switch E is the commutetingswitch, which is thrownin one directicn or the other, according as it is desired to operate onalternating or directv invention it is possible to use only urrent. Foralternatingcurrent operation. witch E is thrown toward the left,connecting trolley B to one terminal or" the auto- ?or direct-currentopera in the opposite .e the r:

rection, cennecting trolley represents the reversing switch. Controllingswitch G is shown with four positions,

two for direct. In its two alternating-current.

two for alternating current operation,v and positions, indicated by theri ht-hand movable contacts, the switch ma es no change in theconnections of the motors to each other, but simply varies the point ofconnection of the motors to the auto-transformer D, as will be evidentfrom an inspection of the figure.

The motor connections forv alternatingcurrent operation are shown inFig. 2. 7

' ingsis twice t e current in each armature.

,By means of this c'onnectiona compensating winding having only half theusual number of turns maybe employed. For directcurrent operation theswitch I H is arranged to connect the four motors in seriesand inparallel. The series connec- '.'tion is shown in Fig. 3, in. which allfour motors have their "fields, compensating windings and series. Withthis connection, only half compensation is obtained, but fordirectcurrent operation at low speeds, this undercompensation isentirely immaterial. In

, the second position of the switch the connections shown in Fig. 4 areestablished, which are identical with those shown in Fig. 2, except thatthe motor circuit is connected directly to trolley, instead of to theauto-transformer. Thus, for full-speed direct-current operation, iullcompensation is obtained in precisely the same manner as it is obtainedfor both speeds in alternatingcurrent operation. a

Althou h 1 have shown only two positions of the switch G for operationon each kind ofqcurrent, it will be understood that this switchmaybe'modified as desired.

The parallel connection of the armatures with series connection ofthecompensatin windings possesses an advantage additiona to thosealready pointed out, since if the driving-wheels, to which any one motoris connected, begin to slip so that the motor speeds up, the current ofthat motor will be out down by the rise in counter-electrosraeae whichpasses throug ,winding of the first motor, so that slipping claims tocover-all modifications armatures all connected inv motive fbrce,while-the motor in parallel with it will be taking full current, all ofmotor is automatically over-compensated," which helps to preventcommutatmntroubles at the high-speed due to the slip. V

I do not desire to limit myself to the particular construction andarrangement of partshere shown, but aim in the appended within the scopeof my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is, 1. In combination, a plurality .of motors of the commutatortype, each having a compensating windin with a smallennumber of turnsthan the e ective turns of the armature, and means for connectingaplurality of motorsiwith their armatures inparallel with thecompensating ch are each other and their compensating windings in serieswith each other andwiththev armatures.

2. A pluralityof motors of the commutator type, each having acompensating windin with a smaller number of turnsthan the efiectiveturns of the armature, said motors being connected with their armaturesin parallel with each other and their compensating windings in serieswith each other and with the armatures. i

3. In combination, a plurality of motors 1 of the commutator type, eachhaving a com-' pensating windin with a smaller number of turns than thee ective turns of the armature, and a controlling switch for said motorsarranged in its full-speed position to connect a plurality'ol' motorswith their armatures in parallel with each other and with theircompensating windings in series with each other and with the armatures.

4. The method'oi operating a plurality of motors of the commutator type,each having a compensating winding with a smaller number of turns thanthe efiective turns of the armature, which consists inconnecting aplurality of the motors with their armatures'in parallel with each otherand their compensating windings in series witheach other and with thearmatures.

In witness whereof, \I have hereunto set my hand this 7th day of July,1906.

ERNST F. W. ALEXANDERSON.

Witnesses: BENJAMIN B. HULL, HELEN Onronn.

